How Food Affects Blood Sugar

Trying to control your blood sugar? Learn which foods contribute to high blood sugar and which ones should be included in a low glycemic diet.

By Elizabeth Shimer Bowers

Medically reviewed by Lindsey Marcellin, MD, MPH

If you or a loved one has diabetes, you know how important it is to stay in control of your blood glucose (sugar). Normally, the body is able to regulate blood glucose levels effectively by producing more or less insulin, a hormone that helps to effectively control blood sugar. But when you have diabetes, your body doesn’t produce enough insulin. “In many cases, people with diabetes require insulin treatment to get their blood sugar under control,” says Alison Massey, MS, RD, a certified diabetes educator at the Center for Endocrinology at Mercy Medical Center in Baltimore. In some people with diabetes, insulin is still produced but the body becomes less sensitive to it, making treatment necessary.

When you’re living with diabetes, episodes of high blood sugar can occur for a number of reasons, including illness, stress, exercise, and medication side effects, Massey says. But the most prominent factor in blood sugar control iswhat you eat.

Some foods — like carbohydrates — are of particular concern. “Carbohydrate foods are digested and broken down into glucose (blood sugar) in the bloodstream, which the body uses and stores for energy,” Massey explains. Many carbohydrates have what is called a “high glycemic index,” meaning they’re foods that quickly spike blood sugar to higher levels. Foods high in protein and fat and carbohydrates that are more slowly digested, such as bread made from sprouted grains, also cause blood sugar to rise, but much less significantly. These foods are often referred to as having a “low glycemic index.”

Therefore, what and how much you eat can mean the difference between poor or good blood sugar control. Here’s some information to help you understand the importance of a diabetes diet so you can best control blood sugar:

Create the right plate. “Fill half of your plate with non-starchy, low-calorie vegetables, a quarter of your plate with protein, and a quarter of your plate with whole-grain carbohydrates,” says Ann Williams, PhD, RN, a certified diabetes educator and a research associate professor at Case Western Reserve University in Cleveland, Ohio. For example, dinner might look like: A small piece of grilled fish or chicken for protein, a hearty serving of steamed broccoli and carrots, and a small helping of brown rice for carbohydrates. “This is very simple to follow and will cause you to eat less food in the long run because you’re filling up on lower-calorie vegetables rather than foods that raise blood sugar.”

Skip the starchy vegetables. “Non-starchy vegetables, such as broccoli, green peppers, and mushrooms, tend to be high in nutrients and lower in carbohydrates,”Massey says. That makes them good choices for a low glycemic diet. Bad choices? Starchier vegetables like potatoes, corn, and peas.

Eat fiber-rich carbohydrates. To help control blood sugar, choose carbohydrates made from whole grains, Dr. Williams says. That's because "foods made with whole grains and other high-fiber choices will generally go into the bloodstream more slowly than a food made with white rice or white flour,” so the impact on your blood sugar level will not be as severe.

Go “big.” “Foods with a smaller particle size will be absorbed and converted into blood glucose faster than foods with a larger particle size,” she says.“So to control blood sugar, go for cracked wheat cereal, which normally has a large particle size, for example, and potatoes in chunks rather than mashed.”

Cook al dente. “Foods cooked more thoroughly go into the body faster than foods cooked less thoroughly,” Williams says. Therefore, to more carefully control blood sugar, go for pasta and even potatoes cooked al dente —still firm — rather than overcooked and mushy. Of course, certain foods, like poultry, should always be well-cooked.

Eat at regular intervals. “For most people with diabetes, it’s a good idea to eat approximately every four hours to control blood sugar,” Williams says. “It’s possible to adjust your insulin dose so you can go longer between meals, but you don’t want to become ravenously hungry and then overeat, so around four hours is a good rule of thumb.”

Don’t deprive yourself. “If you’re really craving ice cream or another food that raises blood sugar, have a small serving, really enjoy it, and get it over with— don’t wait three days until you give in and eat a whole container,” Williams says. “Of course, you shouldn’t have foods like this every day, but diabetes is a game of averages, not a game of perfection, so you won’t totally ruin your overall blood sugar control if you splurge on one occasion.”